Biology subjects

Herrmann, B.

Publications and source records attributed to Herrmann, B..

4 recordsLinked to original sources

bioRxiv2018

Dynamics of spontaneous alpha activity correlate with language ability in young children

Early childhood is a period of tremendous growth in both language ability and brain maturation. To understand the dynamic interplay between neural activity and spoken language development, we used resting-state EEG recordings to explore the relation between alpha oscillations (7-10 Hz) and oral language ability in 4- to 6-year-old children with typical development (N=41). Three properties of alpha oscillations were investigated: a) alpha power using spectral analysis, b) flexibility of the alpha frequency quantified via the oscillation's moment-to-moment fluctuations, and c) scaling behavior of the alpha oscillator investigated via the long-range temporal correlation in the alpha-amplitude time course. All three properties of the alpha oscillator correlated with children's oral language abilities. Higher language scores were correlated with lower alpha power, greater flexibility of the alpha frequency, and longer temporal correlations in the alpha-amplitude time course. Our findings demonstrate a cognitive role of several properties of the alpha oscillator that has largely been overlooked in the literature.

neuroscience↗

bioRxiv2018

Aging alters envelope representations of speech-like sounds in the inferior colliculus

Hearing impairment in aging is thought to arise from impaired temporal processing in auditory circuits. We used a systems-level (scalp recordings) and a microcircuit-level (extracellular recordings) approach to investigate how aging affects the sensitivity to temporal envelopes of speech-like sounds in rats. Scalp-recorded potentials suggest an age-related increase in sensitivity to temporal regularity along the ascending auditory pathway. The underlying cellular changes in the midbrain were examined using extracellular recordings from inferior colliculus neurons. We observed an age-related increase in sensitivity to the sounds onset and temporal regularity (i.e., periodicity envelope) in the spiking output of inferior colliculus neurons, relative to their synaptic inputs (local field potentials). This relative enhancement for aged animals was most prominent for multi-unit (relative to single-unit) spiking activity. Spontaneous multi-unit, but not single-unit, activity was also enhanced in aged compared to young animals. Our results suggest that aging is associated with altered sensitivity to a sounds temporal regularities, and that these effects may be due to increased gain of neural network activity in the midbrain.

neuroscience↗

bioRxiv2018

Neural signatures of the processing of temporal patterns in sounds

The ability to detect regularities in sound (i.e., recurring structure) is critical for effective perception, enabling, for example, change detection and prediction. Two seemingly unconnected lines of research concern the neural operations involved in processing regularities: one investigates how neural activity synchronizes with temporal regularities (e.g., frequency modulation; FM) in sounds, whereas the other focuses on increases in sustained activity during stimulation with repeating tone-frequency patterns. In three electroencephalography studies with male and female human participants, we investigated whether neural synchronization and sustained neural activity are dissociable, or whether they are functionally interdependent. Experiment I demonstrated that neural activity synchronizes with temporal regularity (FM) in sounds, and that sustained activity increases concomitantly. In Experiment II, phase coherence of FM in sounds was parametrically varied. Although neural synchronization was more sensitive to changes in FM coherence, such changes led to a systematic modulation of both neural synchronization and sustained activity, with magnitude increasing as coherence increased. In Experiment III, participants either performed a duration categorization task on the sounds, or a visual object tracking task to distract attention. Neural synchronization was observed irrespective of task, whereas the sustained response was observed only when attention was on the auditory task, not under (visual) distraction. The results suggest that neural synchronization and sustained activity levels are functionally linked: both are sensitive to regularities in sounds. However, neural synchronization might reflect a more sensory-driven response to regularity, compared with sustained activity which may be influenced by attentional, contextual, or other experiential factors.\n\nSignificance statementOptimal perception requires that the auditory system detects regularities in sounds. Synchronized neural activity and increases in sustained neural activity both appear to index the detection of a regularity, but the functional interrelation of these two neural signatures is unknown. In three electroencephalography experiments, we measured both signatures concomitantly while listeners were presented with sounds containing frequency modulations that differed in their regularity. We observed that both neural signatures are sensitive to temporal regularity in sounds, although they functionally decouple when a listener is distracted by a demanding visual task. Our data suggest that neural synchronization reflects a more automatic response to regularity, compared with sustained activity which may be influenced by attentional, contextual, or other experiential factors.

neuroscience↗

bioRxiv2017

Temporal expectation modulates cortical dynamics of sensory memory

Increased memory load is often signified by enhanced neural oscillatory power in the alpha range (8-13 Hz), taken to reflect inhibition of task-irrelevant brain regions. The corresponding neural correlates of memory decay, however, are not yet well-understood. Here, we investigated auditory sensory memory decay using a delayed matching-to-sample task with pure-tone sequences. First, in a behavioral experiment we modeled memory behavior over six different delay-phase durations. Second, in a magnetoencephalography (MEG) experiment, we assessed alpha-power modulations over three different delay-phase durations. In both experiments, the temporal expectation for the to-be-remembered sound was manipulated, so that it was either temporally expected or not. In both studies, memory performance declined over time but this decline was less strong under a more precise temporal expectation. Similarly, patterns of alpha power in and alpha-tuned connectivity between sensory cortices changed parametrically with delay duration (i.e., decrease in occipito-parietal regions, increase in temporal regions). Notably, temporal expectation counteracted alpha-power decline in heteromodal brain areas (i.e., supramarginal gyrus), in line with its memory-decay counteracting effect on performance. Correspondingly, temporal expectation also boosted alpha connectivity within attention networks known to play an active role during memory maintenance. The present data outline how patterns of alpha power orchestrate sensory memory decay, and encourage a refined perspective on alpha power and its inhibitory role across brain space and time.\n\nSignificance StatementOur sensory memories of the physical world fade quickly. We show here that this decay of sensory memory can be counteracted by so-called temporal expectation, that is, knowledge of when to expect the to-be-remembered sensory event (here, brief sound patterns). We also show that distinct patterns and modulations of neural oscillations in the \"alpha\" (8-13 Hz) range index both, the degree of memory decay, and any benefit from temporal expectation, both of which affect memory performance. Critically, spatially distributed cortical patterns of alpha power, with opposing effects in auditory vs. visual sensory cortices and alpha-tuned connectivity changes within supramodal attention networks, reflect the allocation of neural resources as sensory memory representations fade.

neuroscience↗